Caption: Biogas advert, China. Biogas. Advert for biogas on car in China, passing in front of a building with a large statue of Chairman Mao. Biogas refers to gases produced by the decomposition of biological waste. In China, biogases such as methane are being produced from the digestion and fermentation of animal manure and faeces. The production is managed by the Biogas Institute of the Ministry of Agriculture, China.